Given how weak and persecuted Christianity was before Constantine, I doubt that there was such a Christian empire. The people in Arabia, especially those who traded in frankincense (I forget what the civilization was called) borrowed heavily from different cultures they traded with such as the Greeks and the Romans. If such a depiction is Christian in origin, they may have just met Christians and liked their architecture.
But if we walk in the light, as He is in the light, we have fellowship with one another, and the blood of Jesus, His Son, purifies us from all sin.
